package org.xjh.selectimagevideo.itemdecoration;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.support.v7.widget.GridLayoutManager;
import android.support.v7.widget.RecyclerView;
import android.support.v7.widget.StaggeredGridLayoutManager;
import android.view.View;

/**
 * Grid布局itemecoration
 * Created by jianhongxu on 2017/6/20.
 */

public class DividerGridItemDecoration extends RecyclerView.ItemDecoration {
    private static final int[] ATTRS = new int[]{android.R.attr.listDivider};
    private Drawable mDivider;

    public DividerGridItemDecoration(Context context) {
        final TypedArray array = context.obtainStyledAttributes(ATTRS);
        mDivider = array.getDrawable(0);
        array.recycle();
    }

    @Override
    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
        drawHorizontal(c, parent);
        drawVertical(c, parent);
    }

    private int getSpanCount(RecyclerView parent) {
        //列数
        int spanCount = -1;
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            spanCount = ((GridLayoutManager) layoutManager).getSpanCount();
        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
            spanCount = ((StaggeredGridLayoutManager) layoutManager).getSpanCount();
        }
        return spanCount;
    }

    private void drawHorizontal(Canvas c, RecyclerView parent) {
        int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int left = child.getLeft() - params.leftMargin;
            final int top = child.getBottom() + params.bottomMargin;
            final int right = child.getRight() + params.rightMargin + mDivider.getIntrinsicWidth();
            final int bottom = top + mDivider.getIntrinsicHeight();
            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    private void drawVertical(Canvas c, RecyclerView parent) {
        final int childCount = parent.getChildCount();
        for (int i = 0; i < childCount; i++) {
            final View child = parent.getChildAt(i);
            final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child.getLayoutParams();
            final int left = child.getRight() + params.rightMargin;
            final int top = child.getTop() - params.topMargin;
            final int right = left + mDivider.getIntrinsicWidth();
            final int bottom = child.getBottom() + params.bottomMargin;

            mDivider.setBounds(left, top, right, bottom);
            mDivider.draw(c);
        }
    }

    private boolean isLastColum(RecyclerView parent, int position, int spanCount,
                                int childCount) {
        RecyclerView.LayoutManager manager = parent.getLayoutManager();
        if (manager instanceof GridLayoutManager) {
            if ((position + 1) % spanCount == 0) {// 如果是最后一列，则不需要绘制右边
                return true;
            }
        } else if (manager instanceof StaggeredGridLayoutManager) {
            int orientation = ((StaggeredGridLayoutManager) manager).getOrientation();
            if (orientation == StaggeredGridLayoutManager.VERTICAL) {
                if ((position + 1) % spanCount == 0) {// 如果是最后一列，则不需要绘制右边
                    return true;
                }
            } else {
                childCount = childCount - childCount % spanCount;
                if (position >= childCount) {// 如果是最后一列，则不需要绘制右边
                    return true;
                }
            }
        }
        return false;
    }

    private boolean isLastRow(RecyclerView parent, int position, int spanCount,
                              int childCount) {
        RecyclerView.LayoutManager layoutManager = parent.getLayoutManager();
        if (layoutManager instanceof GridLayoutManager) {
            childCount = childCount - childCount % spanCount;
            if (position >= childCount) {// 如果是最后一行，则不需要绘制底部
                return true;
            }
        } else if (layoutManager instanceof StaggeredGridLayoutManager) {
            int orientation = ((StaggeredGridLayoutManager) layoutManager).getOrientation();

            // StaggeredGridLayoutManager 且纵向滚动
            if (orientation == StaggeredGridLayoutManager.VERTICAL) {
                childCount = childCount - childCount % spanCount;
                // 如果是最后一行，则不需要绘制底部
                if (position >= childCount) {
                    return true;
                }
            }else{   // StaggeredGridLayoutManager 且横向滚动
                // 如果是最后一行，则不需要绘制底部
                if((position+1)%spanCount==0){
                    return true;
                }
            }
        }
        return false;
    }

    @Override
    public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
        int spanCount =getSpanCount(parent);
        int childCount = parent.getAdapter().getItemCount();
        if(isLastRow(parent,parent.getChildLayoutPosition(view),spanCount,childCount)){// 如果是最后一行，则不需要绘制底部
            outRect.set(0,0,mDivider.getIntrinsicWidth(),0);
        }else if(isLastColum(parent,parent.getChildLayoutPosition(view),spanCount,childCount)){// 如果是最后一列，则不需要绘制右边
            outRect.set(0,0,0,mDivider.getIntrinsicHeight());
        }else{
            outRect.set(0,0,mDivider.getIntrinsicWidth(),mDivider.getIntrinsicHeight());
        }
    }
}
